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Mercury,
January/February 2005 Table of Contents
by
Thomas J. Sherrill
A solar-monitoring
telescope is being placed "in orbit around L1." The James
Webb Space Telescope (successor to the Hubble Space Telescope) is
planned for launch in the year 2011 to "L2." In the past
there was a group of space habitation enthusiasts called the "L5
Society" (now part of the National Space Society). The "L"
in these terms stands for Lagrangian, and the designations L1, L2,
L3, L4, and L5 are the so-called "Lagrangian points."
But what exactly are these points, and what makes them such special
destinations for spacecraft?
Table
1. Six missions and counting...... The future of the Lagrangian
points as space destinations seems assured as new generations of
space-based observatories in the planning stage seriously consider
using L2 halo orbits because of their attractive operational environment.
In a few cases the Lagrangian option is only one of several. Launch
dates become more uncertain for farther-down-the-line missions,
as forerunner programs may be delayed or extremely ambitious projects
find that technology has a lot of catching up to do. The question
marks in the Lagrangian Point column indicate that L1 or L2 may
not be the most preferred orbital option.
Past
and Current Missions:
| Mission |
Operational |
At
LP |
Lagrang
Pt |
Program |
Science
Mission |
| ISEE-3/ICE |
8/78
- 5/97 |
4
yrs |
L1 |
Explorer |
(International
Sun-Earth Explorer / International Comet Explorer) Investigate
solar-terrestrial relationships, solar wind, earth's magnetosphere,
and cosmic rays |
| Wind |
11/94
- pres |
1
yr |
L1 |
Global
Geospace Science Initiative |
(GGSI
= U.S. portion of International Solar-Terrestrial Physics Program
[ISTP]) Study solar wind before and as it encounters earth's
day-side magnetosphere |
| SOHO |
12/95
- pres |
8.8
yrs |
L1 |
ESA/NASA/COSTR |
(Solar
and Heliospheric Observatory, part of Collaborative Solar-Terrestrial
Research Program of the ISTP) Study solar corona, structure
and interior dynamics |
| ACE |
8/97
- pres |
7
yrs |
L1 |
Explorer |
(Advanced
Composition Explorer) Determine composition of interplanetary
and interstellar particles from solar wind particles to high-energy
galactic cosmic rays |
| WMAP |
6/01
- pres |
3.3
yrs |
L2 |
Medium
Class Explorer |
(Wilkinson
Microwave Anisotropy Probe) Map cosmic microwave background
temperature to high angular resolution and sensitivity |
| Genesis |
8/01
- 9/04 |
2.5
yrs |
L1 |
Discovery |
Collect
solar wind particles and return them to earth for retrieval
|
Proposed
Future Missions:
| Mission |
Launch |
Duration |
Lagrang
Pt |
Program |
Science
Mission |
| Triana |
TBR |
2-5
yrs |
L1 |
SMEX-Lite |
Full-time
observation of whole earth; s/c built and tested, in storage,
unlikely to fly |
| LISA
Pathfinder |
2006-7 |
6
mos - 1 yr |
L1
or L2 |
ESA |
Precursor
to Laser Interferometry Space Antenna (LISA) mission, to demonstrate
precise formation flying and measurements to detect gravitational
waves |
| Herschel
(FIRST) |
2007 |
>
3 yrs |
L2 |
ESA
Cornerstone |
(Formerly
Far Infrared and Submillimeter Telescope) Photometric and spectroscopic
study of early galaxy and star formation |
| Planck |
2007 |
21
mos |
L2 |
ESA
Horizon 2000 |
(Formerly
COBRAS/SAMBA -- to be launched with Herschel) Map cosmic microwave
background temperature to highest angular resolution and sensitivity |
| SPICA
(H2L2) |
2010 |
3
yrs |
L2 |
Institute
of Space & Astronaut Sci |
(Space
Infrared Telescope for Cosmology and Astrophysics, aka HII/L2
-- Japanese mission) IR observatory, successor to ASTRO-F/IRIS
infrared survey mission |
|
Geostorm |
2010? |
>
5 yrs |
<
L1 |
NOAA/NASA/DoD |
Monitor
solar dynamics, flare activity, warn of geomagnetic storms (spacecraft
maintained 3.3 million km beyond L1 using solar sail techniques)
|
|
SPIRIT |
> 2010 |
5
yrs |
L2 |
Origins |
(Space
Infrared Interferometric Telescope) Precursor to SPECS, structurally
connected interferometer to demonstrate key far infrared interferometry
technologies |
|
JWST |
2011 |
5-10
yrs |
L2 |
Origins |
(James
Webb Space Telescope, formerly Next Generation Space Telescope)
Successor to HST, telescope operating from visible to infrared |
|
MAXIM Pathfinder |
2011-15 |
3-5
yrs |
L1
or L2? |
New
Millennium Program |
Precursor
to MAXIM, separate optics and detector spacecraft in formation
flight to demonstrate X-ray interferometry |
| GAIA |
2012 |
5-10
yrs |
L2 |
ESA
Cornerstone |
(Global
Astrometric Interferometer for Astrophysics) Utilize visible-wavelength
interferometry to measure positions and characteristics of 1
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